One of his best-known works is the graphic adventure Loom (1990). He also worked with Ron Cobb on Loadstar: The Legend of Tully Bodine (1994). He participated in the creation of an early version of the graphic adventure The Dig (1995). That version was eventually canceled, but some of its features made it into the game's final release.

Moriarty is Professor of Interactive Media and Game Development at Worcester Polytechnic Institute.